Center-Notched Strap for Citizen CA0313-07E
A Citizen CA0313-07E will not take a strap off the shelf. The case is built so the band has to sit into it rather than under it, which means the strap end needs a tongue cut into the middle and shoulders left either side. An order from Georgia came in with the three numbers that describe that shape already taken — X 25mm, Y 16mm, Z 6mm — and a black Epsom strap was cut to them at 80/130mm.
What was built
| Watch | Citizen CA0313-07E |
| Leather | Black Epsom |
| Cut | Center-notched — X 25mm, Y 16mm, Z 6mm |
| Length | 80/130mm (3.1 in / 5.1 in) |
Why these choices
The three measurements are not interchangeable, and the middle one does most of the work. X is the full width of the strap end. Y is the width of the tongue that enters the case. Z is how far back the notch is cut. On this build Y came in at 16mm against a 25mm end, with the notch running 6mm deep — a deeper cut than most, which tells you the case swallows a good length of the strap before the shoulders make contact. Get Z wrong by two millimeters and the strap either bottoms out early or leaves a visible gap.
This is why we ask for your figures rather than looking the watch up. Reference numbers are not a reliable guide to notch geometry: case backs get replaced, bezels differ between production runs, and catalog lug widths describe the gap, not the shape of the recess around it. A jeweler can take all three in a few minutes, and it is worth doing before ordering, because a notch cannot be recut larger once it is wrong.
Black Epsom suits a notched build for a practical reason as much as a visual one. Epsom is stamped-grain calfskin, the same leather Hermès uses for bags — light, scratch-resistant, and firm enough to hold a cut edge. The notched shoulders are exposed edges that sit right against the case, so they get handled and rubbed every time the watch goes on. A softer hide rounds off there within a few months; Epsom keeps the shape it was cut to.
Common questions
What do you need to make a center-notched strap for a Citizen CA0313-07E?
X, Y and Z — the full end width, the tongue width, and the notch depth. Send those three and we cut to them. A photo of the watch from the side helps us sanity-check the numbers before anything is cut.
What is the difference between center-notched and corner-notched?
Center-notched leaves a tongue in the middle with shoulders either side, measured X, Y and Z. Corner-notched removes the two outer corners instead and is measured A, B and C — that is the Cartier Santos pattern.
Notched straps are cut to your measurements and made to order — allow two to three weeks to delivery. Start with the custom center-notched strap, see the full notched strap range, compare the Epsom leathers, or browse black leather watch straps.